Buffer material

ABSTRACT

A buffer material of the present disclosure is a material including cellulose fibers and a binding material that binds the cellulose fibers, in which the binding material is a natural component and a proportion of the binding material in the buffer material is 10.0% by mass or greater and 30.0% by mass or less. It is preferable that the buffer material of the present disclosure have a thickness of 1.0 mm or greater and 100 mm or less and that the buffer material have a density of 0.02 g/cm 3  or greater and 0.20 g/cm 3  or less. It is preferable that the binding material contain a shellac resin. It is preferable that a content of lignin in the cellulose fibers be 5.0% by mass or less.

The present application is based on, and claims priority from JPApplication Serial Number 2021-124154, filed Jul. 29, 2021, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a buffer material.

2. Related Art

In recent years, there has been a demand for a buffer material with alow environmental load in place of plastic materials. In the relatedart, a processing method of reusing used paper has been known. Forexample, JP-A-9-296398 suggests a processing method of crushing usedpaper into fibers and molding the fibers using polypropylene or a vinylacetate emulsion as a solidifying material. Further, JP-A-2002-172728suggests a method of coating one surface or both surfaces of a paperbase material with a shellac resin which is a biologically producednatural resin obtained by purifying an acid ester resinous substancesecreted by scale insects, to process a packaging material.

However, in the processing method disclosed in JP-A-9-296398, since thesolidifying material is not a naturally derived material, reduction inenvironmental load is insufficient. In the processing method disclosedin JP-A-2002-172728, the water resistance and the oil resistance areimproved by dissolving the shellac resin in water, alcohol, or the likeand coating the paper base material with the mixture, but the strengthof the packing material is not described. Therefore, a buffer materialwith a further reduced environmental load and satisfactory strength isrequired.

SUMMARY

The present disclosure has been made to solve the above-describedproblems and can be realized as the following aspect.

According to an aspect of the present disclosure, there is provided abuffer material including cellulose fibers, and a binding material thatbinds the cellulose fibers, in which the binding material is a naturalcomponent and a proportion of the binding material in the buffermaterial is 10.0% by mass or greater and 30.0% by mass or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing an example of a production devicecapable of producing a sheet-like buffer material.

FIG. 2A is a view showing an example of the shape of a molding die usedfor producing a buffer material.

FIG. 2B is a view showing an example of the shape of a molding die usedfor producing a buffer material.

FIG. 2C is a view showing an example of the shape of a molding die usedfor producing a buffer material.

FIG. 2D is a view showing an example of the shape of a molding die usedfor producing a buffer material.

FIG. 3 shows stress/strain curves of Examples 1 to 4.

FIG. 4 shows stress/strain curves of Examples 5 to 8.

FIG. 5 shows buffer coefficients/strain curves of Examples 1 to 4.

FIG. 6 shows buffer coefficients/strain curves of Examples 5 to 8.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail.

Examples of the present disclosure will be described in the embodimentsdescribed below. The present disclosure is not limited to the followingembodiments and include various modifications within a range notdeparting from the scope of the present disclosure. Further,configurations described below may not all necessarily be essentialconfigurations. 1. Buffer material

First, a buffer material will be described.

The buffer material of the present embodiment contains a plurality ofcellulose fibers and a binding material that binds the cellulose fibers.Further, the binding material is a natural component and the proportionof the binding material in the buffer material is 10.0% by mass orgreater and 30.0% by mass or less.

With such a configuration, a buffer material with a reducedenvironmental load and satisfactory strength can be provided.

Meanwhile, when the content of the binding material which is a naturalcomponent in the buffer material is less than the lower limit describedabove, the adhesive force of the cellulose fibers cannot be sufficientlyincreased, and thus the strength of the buffer material cannot besufficiently increased. Further, the moldability of the buffer materialis significantly deteriorated, and as a result, the production of thebuffer material becomes difficult.

Further, when the content of the binding material which is a naturalcomponent in the buffer material is greater than the upper limitdescribed above, the buffer effect of the buffer material cannot besufficiently increased. Further, cracks and the like are likely tooccur, and thus the strength is significantly decreased. Further, themoldability of the buffer material is significantly deteriorated, and asa result, the production of the buffer material becomes difficult.

1-1. Cellulose Fibers

The buffer material of the present embodiment contains a plurality ofcellulose fibers.

The cellulose fibers are an abundant material derived from a plant, andit is preferable that the cellulose fibers be used as fibers from theviewpoints of suitably dealing with the environmental problems, savingreserve resources, stably supplying the buffer material, reducing thecost, and the like. Further, the cellulose fibers have a particularlyhigh theoretical strength among various fibers and are also advantageousfrom the viewpoint of improving the strength of the buffer material.

Typically, cellulose fibers are mainly formed of cellulose, but maycontain components other than cellulose. Examples of such componentsinclude hemicelluloses and lignin.

Here, the content of lignin in the cellulose fibers is preferably 5.0%by mass or less, more preferably 3.0% by mass or less, and still morepreferably 1.0% by mass or less.

In this manner, buffering performance, particularly compressioncharacteristics, of the buffer material is further improved.

The content of the cellulose in the cellulose fibers is preferably 50.0%by mass or greater, more preferably 60.0% by mass or greater, and stillmore preferably 80.0% by mass or greater.

For example, fibers which have been subjected to a bleaching treatmentor the like may be used as the cellulose fibers. Further, the cellulosefibers may have been subjected to a treatment such as an ultravioletirradiation treatment, an ozone treatment, or a plasma treatment.

As the cellulose fibers, chemical cellulose fibers such as organiccellulose fibers, inorganic cellulose fibers, and organic-inorganiccomposite cellulose fibers may be used in addition to the naturalcellulose fibers such as animal cellulose fibers and plant cellulosefibers. More specifically, examples of the cellulose fibers includecellulose fibers consisting of cellulose, cotton, cannabis, kenaf,linen, ramie, jute, manila hemp, sisal hemp, conifer, and hardwood.These cellulose fibers may be used alone or in the form of a mixture asappropriate, or may be used as regenerated cellulose fibers which havebeen purified or the like. Further, the cellulose fibers may besubjected to various surface treatments.

The average length of the cellulose fibers is not particularly limited,but is preferably 10 μm or greater and 50 mm or less, more preferably 20μm or greater and 5.0 or less, and still more preferably 30 μm orgreater and 3.0 or less in terms of the length-weighted averagecellulose fiber length.

In this manner, the stability of the shape of the buffer material, thestrength of the buffer material, and the like can be further improved.Further, the buffering performance of the buffer material can be furtherimproved.

When the cellulose fibers contained in the buffer material of thepresent embodiment are considered to be one independent cellulose fiber,the average thickness thereof is preferably 1.0 μm or greater and 1000μm or less and more preferably 2.0 μm or greater and 100.0 μm or less.

In this manner, the stability of the shape of the buffering material,the strength of the buffer material, and the like can be furtherimproved. Further, the buffering performance of the buffer material canbe further improved. Further, it is possible to more effectively preventthe surface of the buffer material from being unexpectedly uneven.

Further, when a cross section of the cellulose fiber is not circular, acircle having the same area as the area of the cross section is assumed,and the diameter of the circle is used as the thickness of the cellulosefiber.

The average aspect ratio of the cellulose fibers, that is, the averagelength with respect to the average thickness is not particularlylimited, but is preferably 10 or greater and 1000 or less and morepreferably 15 or greater and 500 or less.

In this manner, the stability of the shape of the buffering material,the strength of the buffer material, and the like can be furtherimproved. Further, the buffering performance of the buffer material canbe further improved. Further, it is possible to more effectively preventthe surface of the buffer material from being unexpectedly uneven.

In the present specification, the term “cellulose fibers” denote asingle cellulose fiber or an aggregate of a plurality of cellulosefibers. Further, the cellulose fibers may be cellulose fibers loosenedinto fibers by performing a defibration treatment on a material to bedefibrated, that is, a defibrated material. Examples of the material tobe defibrated here include cellulose fibers obtained by being entangledor bound, such as pulp sheets, paper, used paper, tissue paper, kitchenpaper, cleaners, filters, liquid absorbing materials, sound absorbingbodies, buffer materials, mats, and corrugated cardboard.

The content of the cellulose fibers in the buffer material is preferably63.0% by mass or greater and 90.0% by mass or less, more preferably67.0% by mass or greater and 88.0% by mass or less, and still morepreferably 72.0% by mass or greater and 86.0% by mass or less.

In this manner, the strength and the buffering performance of the buffermaterial can be further improved.

1-2. Binding Material

The buffer material of the present embodiment contains a bindingmaterial which is a natural component. Hereinafter, the binding materialwhich is a natural component will also be referred to as “naturalbinding material”.

The binding material has a function of binding a cellulose fiber to acellulose fiber and may further have other functions. More specifically,the binding material may have a function of suppressing a componentother than the cellulose fibers, for example, a colorant or the likedescribed below from falling off from the buffer material. Further, apart of the natural binding material contained in the buffer materialmay be contained in a form in which the above-described function is notexhibited.

It is preferable that the natural binding material have thermalplasticity.

In this manner, the natural binding material is melted or softened byapplying heat in the process of producing the buffer material to spreadbetween cellulose fibers, and thus the cellulose fibers are likely to bebound to each other.

The natural binding material is melted or softened preferably at 200° C.or lower and more preferably at 160° C. or lower.

In this manner, the cellulose fibers can be more suitably bound to eachother by carrying out a heat treatment at a relatively low temperature,which is more preferable from the viewpoint of energy saving.

The glass transition temperature of the natural binding material ispreferably 45° C. or higher and 95° C. or lower and more preferably 50°C. or higher and 90° C. or lower.

In this manner, the cellulose fibers can be more suitably bound to eachother by carrying out a heat treatment at a relatively low temperature,which is more preferable from the viewpoint of energy saving. Further,for example, it is possible to effectively prevent the natural bindingmaterial from being unexpectedly softened when the buffer materialstands in a high temperature environment.

Examples of the natural binding material include natural resins such asrosin, dammar, mastic, copal, amber, a shellac resin, dragon tree,sandarac, and colophonium, starch as a natural polymer, and modifiedproducts thereof, and one or two or more selected from among these canbe used in combination, but it is preferable that the natural bindingmaterial contain a shellac resin.

In this manner, the strength and the buffering performance of the buffermaterial can be further improved, and the workability of the buffermaterial can also be further improved.

The proportion of the shellac resin in the entire natural bindingmaterial of the buffer material is preferably 50.0% by mass or greater,more preferably 70.0% by mass or greater, and still more preferably90.0% by mass or greater.

In this manner, the above-described effects are more significantlyexhibited.

The starch is a polymer material obtained by polymerizing a plurality ofα-glucose molecules with glycoside bonds. The starch may be linear orbranched.

For example, starch derived from various plants can be used as thestarch. Examples of raw materials of starch include cereals such ascorn, wheat, and rice, beans such as broad beans, mung beans, and adzukibeans, tubers such as potatoes, sweet potatoes, and tapioca, wildgrasses such as dogtooth violet, bracken, and kadzu, and palms such assago palm.

For example, processed starch or modified starch may be used as thestarch. Examples of the processed starch include acetylated adipic acidcrosslinked starch, acetylated starch, oxidized starch, sodium octenylsuccinate starch, hydroxypropyl starch, hydroxypropylated phosphoricacid crosslinked starch, phosphorylated starch, phosphoric acidmonoesterified phosphoric acid crosslinked starch, urea phosphorylatedesterified starch, sodium starch glycolate, and high amylose cornstarch.Further, examples of the modified starch include pregelatinized starch,dextrin, laurylpolyglucose, cationized starch, thermoplastic starch, andcarbomic acid starch.

The content of the natural binding material in the buffer material maybe 10.0% by mass or greater and 30.0% by mass or less, and is preferably12.0% by mass or greater and 28.0% by mass or less, more preferably14.0% by mass or greater and 25.0% by mass or less, and still morepreferably 15.0% by mass or greater and 22.0% by mass or less.

In this manner, the above-described effects are more significantlyexhibited.

1-3. Other Components

The buffer material of the present embodiment is not limited as long asthe buffer material contains the cellulose fibers and the naturalbinding material, but may further contain other components in additionthe above-described components. Hereinafter, such components will alsobe referred to as “other components”.

Examples of other components include a flame retardant, a colorant, anaggregation inhibitor, a surfactant, a fungicide, a preservative, anantioxidant, an ultraviolet absorbing agent, and an oxygen absorbingagent.

Further, the buffer material of the present embodiment may contain, asother components, binding materials other than the natural bindingmaterial.

Various synthetic resins such as thermoplastic resins, thermosettingresins, and photocurable resins can be used as the binding materialsother than the natural binding material.

Examples of the thermoplastic resins among the synthetic resins includean AS resin, an ABS resin, polypropylene, polyethylene, polyvinylchloride, polystyrene, an acrylic resin, a polyester resin, polyethyleneterephthalate, polyphenylene ether, polybutylene terephthalate, nylon,polyamide, polycarbonate, polyacetal, polyphenylene sulfide, andpolyether ether ketone.

Among the synthetic resins, biodegradable resins such as polylacticacid, polybutylene succinate, and polyhydroxybutanoic acid may be usedas the binding materials other than the natural binding material.

The environmental suitability of the buffer material can be furtherimproved by using the biodegradable resins.

Further, the resins may be, for example, copolymerized or modified.

The content of other components in the buffer material is preferably7.0% by mass or less, more preferably 5.0% by mass or less, and stillmore preferably 3.0% by mass or less.

Particularly when the buffer material contains binding materials otherthan the natural binding material, the content of the binding materialsin the buffer material is preferably 1.0% by mass or less, morepreferably 0.5% by mass or less, and still more preferably 0.1% by massor less.

1-4. Properties and the Like of Buffer Material

The buffer material of the present embodiment may have any size and anyshape. For example, the buffer material may have a sheet shape or athree-dimensional shape.

Further, the buffer material of the present embodiment may be, forexample, processed into a predetermined three-dimensional shape byperforming treatments, such as molding, cutting, bending, notching,organizing, and the like as necessary, on the sheet-like buffer materialwhich has been prepared in advance, using a molding die.

As described above, when the buffer material has a three-dimensionalshape and is produced from a sheet-like buffer material, thethree-dimensional buffer material may be produced by superimposing aplurality of sheet-like buffer materials.

The thickness of the buffer material, that is, the thickness of aportion formed of the material containing cellulose fibers and thenatural binding material is not particularly limited, but is preferably1.0 mm or greater and 100 mm or less, more preferably 1.5 mm or greaterand 30 mm or less, and still more preferably 2.0 mm or greater and 20 mmor less.

In this manner, the strength and the rigidity of the buffer material canbe further improved. Further, for example, the workability when thesheet-like buffer material is processed into a buffer material having athree-dimensional shape by carrying out a process of deep drawing or thelike can be further improved, and occurrence of wrinkles or breakage canbe more effectively prevented.

The density of the buffer material is not particularly limited, but ispreferably 0.02 g/cm³ or greater and 0.20 g/cm³ or less, more preferably0.03 g/cm³ or greater and 0.15 g/cm³ or less, and still more preferably0.05 g/cm³ or greater and 0.11 g/cm³ or less.

In this manner, the strength and the rigidity of the buffer material canbe further improved. Further, the durability of the buffer materialagainst an impact can be further improved. Further, for example, theworkability when the sheet-like buffer material is processed into abuffer material having a three-dimensional shape by carrying out aprocess of deep drawing or the like can be further improved, andoccurrence of wrinkles or breakage can be more effectively prevented.

Particularly when the buffer material satisfies the above-describedconditions for the thickness and the above-described conditions for thedensity, the effects obtained by satisfying the conditions aresynergistically enhanced so that the above-described effects are moresignificantly exhibited.

The basis weight of the buffer material is not particularly limited, butis preferably 100 g/m² or greater and 600 g/m² or less, more preferably150 g/m² or greater and 500 g/m² or less, and still more preferably 150g/m² or greater and 400 g/m² or less.

In this manner, the strength and the rigidity of the buffer material canbe further improved. Further, the durability of the buffer materialagainst an impact can be further improved. Further, for example, theworkability when the sheet-like buffer material is processed into abuffer material having a three-dimensional shape by carrying out aprocess of deep drawing or the like can be further improved, andoccurrence of wrinkles or breakage can be more effectively prevented.

The BET specific surface area of the buffer material is not particularlylimited, but is preferably 0.30 m²/g or greater and 0.50 m²/g or less,more preferably 0.33 m²/g or greater and 0.47 m²/g or less, and stillmore preferably 0.35 m²/g or greater and 0.45 m²/g or less.

The BET specific surface area thereof decreases as the amount of thebinding material such as a shellac resin to adhere to the surface of thefiber increases. The strength of the fibers increases as the adhesionamount increases, and thus effects that make the buffer materialpreferable can be obtained.

Further, the buffer material of the present embodiment may have aportion formed of a material that does not satisfy the above-describedconditions in addition to a portion formed of a material that satisfiesthe above-described conditions. In this case, examples of the portionformed of a material that does not satisfy the above-describedconditions include a core material and a coating layer. Here, theproportion of the material that satisfies the above-described conditionsin the entire buffer material is preferably 50% by volume or greater,more preferably 80% by volume or greater, and still more preferably 90%by volume or greater. 2. Method of producing buffer material

Next, a method of producing the buffer material will be described.

The method of producing the buffer material of the present embodimentincludes a heating and pressing step of heating and pressing acomposition for producing a buffer material which is a compositioncontaining the cellulose fibers and the natural binding material.Further, the proportion of the natural binding material in the totalsolid content constituting the composition for producing a buffermaterial is 10.0% by mass or greater and 30.0% by mass or less.

In this manner, the buffer material as described above, that is, thebuffer material with a reduced environmental load and satisfactorystrength can be suitably produced.

2-1. Composition for Producing Buffer Material

First, the composition for producing the buffer material used in themethod of producing the buffer material of the present embodiment willbe described.

2-1-1. Cellulose Fibers

The composition for producing the buffer material of the presentembodiment contains a plurality of cellulose fibers.

The cellulose fibers described in the section 1-1 can be used as thecellulose fibers contained in the composition for producing the buffermaterial.

In this manner, the same effects as described above can be obtained.

The proportion of the cellulose fibers in the total solid contentconstituting the composition for producing the buffer material ispreferably 63.0% by mass or greater and 90.0% by mass or less, morepreferably 67.0% by mass or greater and 88.0% by mass or less, and stillmore preferably 72.0% by mass or greater and 86.0% by mass or less.

In this manner, the strength and the buffering performance of the buffermaterial to be produced can be further improved.

2-1-2. Natural Binding Material

The composition for producing the buffer material of the presentembodiment contains a natural binding material.

The natural binding material described in the section 1-2 can be used asthe natural binding material contained in the composition for producingthe buffer material.

In this manner, the same effects as described above can be obtained.

When the composition for producing the buffer material contains thenatural binding material in the form of particles, it is preferable thatthe volume average particle diameter of the natural binding material beless than the thickness of the cellulose fibers.

In this manner, the natural binding material and the cellulose fibersare more likely to be uniformly mixed with each other, and thus it ispossible to more effectively prevent the composition of the buffermaterial from being unexpectedly uneven.

The volume average particle diameter of the natural binding material ispreferably 0.8 μm or greater and 100 μm or less and more preferably 1.5μm or greater and 50 μm or less.

The particulate natural binding material can be obtained by beingkneaded using, for example, a kneader, a Banbury mixer, a single-screwextruder, a multi-screw extruder, a twin roll, a triple roll, acontinuous kneader, or a continuous twin roll, pelletized by anappropriate method, and crushed. The natural binding material containsvarious sizes of particles in some cases and may be classified using aknown classification device. Further, the outer shape of the particlesof the natural binding material is not particularly limited, and theparticles may be spherical, disc-like, fibrous, or amorphous.

In the present embodiment, the proportion of the natural bindingmaterial in the total solid content constituting the composition forproducing a buffer material may be 10.0% by mass or greater and 30.0% bymass or less, and is preferably 12.0% by mass or greater and 28.0% bymass or less, more preferably 14.0% by mass or greater and 25.0% by massor less, and still more preferably 15.0% by mass or greater and 22.0% bymass or less.

In this manner, the above-described effects are more significantlyexhibited.

The composition for producing a buffer material may contain the naturalbinding material in any state. For example, the natural binding materialmay be contained in a state of being dissolved in another component orthe like, but it is preferable that the natural binding material becontained in a state of being dispersed in another component,particularly in a state of being dispersed as powder.

In this manner, voids can be suitably formed in the buffer material tobe produced, and thus the buffering performance of the buffer materialcan be more reliably improved.

2-1-3. Liquid Component

The composition for producing a buffer material of the presentembodiment may contain, for example, a liquid component.

When the composition contains a liquid component, for example, thecellulose fibers can enter a suitably loose state in the composition forproducing a buffer material or unexpected uneven distribution or thelike of each component in the composition for producing a buffermaterial can be suitably prevented.

When the composition for producing a buffer material contains a liquidcomponent, the natural binding material may be contained in a state ofbeing dissolved in the liquid component or in a state of being dispersedin the liquid component.

Examples of the liquid component include various organic solvents suchas water, an alcohol-based solvent such as methanol, ethanol, ethyleneglycol, or glycerin, and a ketone-based solvent such as acetone ormethyl ethyl ketone, and one or two or more selected from among thesecan be used in combination.

When the composition for producing a buffer material contains a liquidcomponent, the content of the liquid component in the composition forproducing a buffer material can be set to, for example, 10.0% by mass orgreater and 70.0% by mass or less.

2-1-4. Other Components

The composition for producing a buffer material of the presentembodiment may contain other components in addition to theabove-described components. The other components described in thesection 1-3 can be used as such components.

The proportion of the other components in the total solid contentconstituting the composition for producing a buffer material ispreferably 7.0% by mass or less, more preferably 5.0% by mass or less,and still more preferably 3.0% by mass or less.

Particularly when the composition for producing a buffer materialcontains a binding material other than the natural binding material, theproportion of the binding material in the total solid contentconstituting the composition for producing a buffer material ispreferably 1.0% by mass or less, more preferably 0.5% by mass or less,and still more preferably 0.1% by mass or less.

2-1-5. Properties of Composition for Producing Buffer Material

The composition for producing a buffer material may be in any form ofpowder, a dispersion liquid, a web, or the like.

2-1-6. Preparation of Composition for Producing Buffer Material

The composition for producing a buffer material can be prepared, forexample, by mixing constituent components constituting the compositionfor producing a buffer material.

More specifically, the composition for producing a buffer material canbe prepared, for example, by stirring and mixing defibrated cellulosefibers and the powdery natural binding material. In such a case, forexample, the composition for producing a buffer material can be suitablyprepared by using a device described below.

2-2. Heating and Pressing Step

In the heating and pressing step, the composition for producing a buffermaterial is heated and pressed.

The present step can be performed by a heat press, a heat roller, athree-dimensional molding machine, or the like.

The heating temperature in the present step is preferably 160° C. orhigher, more preferably 165° C. or higher and 250° C. or lower, andstill more preferably 170° C. or higher and 220° C. or lower.

In this manner, the natural binding material can efficiently formbinding of the cellulose fibers while unexpected modification,deterioration, or the like of the constituent components constitutingthe buffer material is effectively prevented, the productivity of thebuffer material can be further improved, and the strength, the bufferingperformance, and the like of the buffer material can be furtherimproved. Further, it is also preferable that the heating temperature bein the above-described ranges even from the viewpoint of energy saving.

The pressing pressure in the present step is preferably 0.50 MPa orless, more preferably 0.01 MPa or greater and 0.45 MPa or less, andstill more preferably 0.05 MPa or greater and 0.40 MPa or less.

In this manner, the natural binding material can efficiently formbinding of the cellulose fibers while the buffer material to be producedis allowed to have a moderate amount of voids, and thus the strength,the buffering performance, and the like of the buffer material can befurther improved. Further, it is also preferable that the pressingpressure be in the above-described ranges even from the viewpoint ofenergy saving.

The heating and pressing time in the present step is preferably 1 secondor longer and 300 seconds or shorter, more preferably 10 seconds orlonger and 60 seconds or shorter, and still more preferably 15 secondsor longer and 45 seconds or shorter.

In this manner, the productivity of the buffer material can be furtherimproved, and the strength, the buffering performance, and the like ofthe buffer material can be further improved. It is also preferable thatthe heating and pressing time be in the above-described ranges even fromthe viewpoint of energy saving.

2-3. Other Steps

The method of producing a buffer material may further include othersteps in addition to the above-described heating and pressing step.Examples of such steps include a cutting step of cutting the producedbuffer material into an appropriate size and an appropriate shape.

2-4. Production Device

Next, a production device that can be used for producing the sheet-likebuffer material will be described.

FIG. 1 is a view schematically illustrating an example of a productiondevice capable of producing the sheet-like buffer material. FIGS. 2A to2D each show an example of the shape of a molding die used forproduction of the buffer material.

As illustrated in FIG. 1 , a production device 100 includes a supplyunit 10, a crushing unit 12, a defibrating unit 20, a sorting unit 40, afirst web forming unit 45, a rotating body 49, a mixing unit 50, anaccumulating unit 60, a second web forming unit 70, a buffer materialforming unit 80, a cutting unit 90, and a humidifying unit 78.

The supply unit 10 supplies the raw material to the crushing unit 12.The supply unit 10 is an automatic charging unit for continuouslycharging the crushing unit 12 with the raw material. The raw material tobe supplied to the crushing unit 12 may contain the cellulose fibers.

The crushing unit 12 cuts the raw material supplied by the supply unit10 in the atmosphere, for example, in the air to form small pieces. Asthe shape and the size of the small pieces, small pieces with a size ofseveral cm square may be exemplified. In the example shown in thefigure, the crushing unit 12 includes crushing blades 14, and the rawmaterial charging the crushing unit 12 can be cut by the crushing blades14. For example, a shredder is used as the crushing unit 12. The rawmaterial cut by the crushing unit 12 is received by a hopper 1 andtransported to the defibrating unit 20 through a pipe 2.

The defibrating unit 20 defibrates the raw material cut by the crushingunit 12. Here, the term “defibrate” denotes that the raw material formedby binding a plurality of cellulose fibers, that is, a material to bedefibrated is loosened into individual cellulose fibers. The defibratingunit 20 also has a function of separating substances, such as resinparticles, an ink, a toner, a filler, and a bleeding inhibitor, adheringto the raw material from the cellulose fibers.

The material after passing through the defibrating unit 20 is referredto as “defibrated material”. In some cases, “defibrated material”contains, in addition to the loosened cellulose fibers, resin particles,a coloring agent such as an ink, a toner, or a filler, and an additivesuch as a bleeding inhibitor or a paper strength enhancer which havebeen separated from the cellulose fibers during loosening of thecellulose fibers. Examples of the resin particles separated from thecellulose fibers include particles containing a resin for binding aplurality of cellulose fibers.

The defibrating unit 20 performs dry type defibration. A treatment ofperforming defibration or the like in the atmosphere, for example, inthe air without performing wet type defibration of dissolving a materialin a liquid such as water in a slurry form is referred to as dry typedefibration. In the present embodiment, an impeller mill is used as thedefibrating unit 20. The defibrating unit 20 has a function ofgenerating an air flow that sucks the raw material and discharges thedefibrated material. In this manner, the defibrating unit 20 can suckthe raw material from an introduction port 22 together with the airflow, perform the defibration treatment, and transport the defibratedmaterial to a discharge port 24 by the air flow generated by itself. Thedefibrated material that has passed through the defibrating unit 20 istransferred to the sorting unit 40 through the pipe 3. Further, as theair flow for transporting the defibrated material to the sorting unit 40from the defibrating unit 20, the air flow generated by the defibratingunit 20 may be used or an airflow generating device such as a blower isprovided and an air flow generated by the device may be used.

The sorting unit 40 introduces the defibrated material defibrated by thedefibrating unit 20 from the introduction port 42 and sorts out thedefibrated material according to the length of the cellulose fibers. Thesorting unit 40 includes a drum portion 41 and a housing unit 43 thataccommodates the drum portion 41. For example, a sieve is used as thedrum portion 41. The drum portion 41 has a net and can divide thedefibrated material into a first sorted material that is cellulosefibers or particles having a size smaller than the size of the mesh ofthe net and thus passing through the net and a second sorted materialthat is cellulose fibers, undefibrated pieces, or lumps having a sizegreater than the size of the mesh of the net and thus not passingthrough the net. For example, the first sorted material is transferredto the mixing unit 50 through the pipe 7. The second sorted material isreturned to the defibrating unit 20 from a discharge port 44 through apipe 8. Specifically, the drum portion 41 is a cylindrical sieverotationally driven by a motor. As the net of the drum portion 41, forexample, a wire net, an expanded metal obtained by expanding a metalplate with cuts, or a punchinig metal in which holes are formed in ametal plate with a press machine or the like is used.

The first web forming unit 45 transports the first sorted materialhaving passed through the sorting unit 40 to the mixing unit 50. Thefirst web forming unit 45 includes a mesh belt 46, a stretching roller47, and a suction unit 48.

The suction unit 48 can suck the first sorted material having passedthrough the opening of the sorting unit 40, that is, the opening of thenet and dispersed in the air, onto the mesh belt 46. The first sortedmaterial is accumulated on the moving mesh belt 46 to form a web V. Thebasic configurations of the mesh belt 46, the stretching roller 47, andthe suction unit 48 are the same as the configurations of a mesh belt72, a stretching roller 74, and a suction mechanism 76 of the second webforming unit 70 described below.

The web V passes through the sorting unit 40 and the first web formingunit 45 and is thus formed in a soft and inflated state due tocontaining a large amount of air. The pipe 7 is charged with the web Vaccumulated on the mesh belt 46, and the web V is transported to themixing unit 50.

The rotating body 49 can cut the web V before the web V is transportedto the mixing unit 50. In the example shown in the figure, the rotatingbody 49 includes a base portion 49 a and protrusions 49 b protrudingfrom the base portion 49 a. The protrusions 49 b have, for example, aplate shape. In the example shown in the figure, four protrusions 49 bare provided and the four protrusions 49 b are provided at equalintervals. Since the base portion 49 a rotates in a direction R, theprotrusions 49 b can rotate using the base portion 49 a as an axis.Since the web V is cut by the rotating body 49, for example, afluctuation in amount of the defibrated material supplied to theaccumulating unit 60 per unit time can be reduced.

The rotating body 49 is provided in the vicinity of the first webforming unit 45. In the example shown in the figure, the rotating body49 is provided in the vicinity of the stretching roller 47 a positionedon the downstream in the path of the web V, that is, next to thestretching roller 47 a. The rotating body 49 is provided at a positionwhere the protrusions 49 b can come into contact with the web V and doesnot come into contact with the mesh belt 46 on which the web V isaccumulated. The shortest distance between the protrusions 49 b and themesh belt 46 is, for example, 0.05 mm or greater and 0.5 mm or less.

The mixing unit 50 mixes the first sorted material having passed throughthe sorting unit 40, that is, the first sorted material transported bythe first web forming unit 45 with an additive containing the naturalbinding material. The mixing unit 50 includes an additive supply unit 52that supplies the additive, a pipe 54 that transports the first sortedmaterial and the additive, and a blower 56. In the example shown in thefigure, the additive is supplied to the pipe 54 through the hopper 9from the additive supply unit 52. The pipe 54 is connected to the pipe7.

The mixing unit 50 allows the blower 56 to generate an air flow so thatthe first sorted material and the additive can be transported whilebeing mixed with each other in the pipe 54. Further, the mechanism ofmixing the first sorted material and the additive is not particularlylimited, and the first sorted material and the additive may be mixed bybeing stirred using a blade rotating at a high speed or may be mixed byusing rotation of a container as in a case of a V type mixer.

A screw feeder as shown in FIG. 1 or a disc feeder which is not shown inthe figure is used as the additive supply unit 52. The additive suppliedfrom the additive supply unit 52 contains the above-described naturalbinding material. The plurality of cellulose fibers have not been boundat the time point when the natural binding material is supplied. Thenatural binding material is partially melted while passing through thebuffer material forming unit 80 so that the plurality of cellulosefibers in the surface region of the buffer material WS are bound.

Further, the additive to be supplied from the additive supply unit 52may contain, in addition to the natural binding material, a colorant forcoloring the cellulose fibers, an aggregation inhibitor for suppressingaggregation of the cellulose fibers or aggregation of the naturalbinding material, and a flame retardant for making the cellulose fibersand the like difficult to burn, depending on the type of the buffermaterial WS to be produced. The composition for producing a buffermaterial which is the mixture having passed through the mixing unit 50,that is, the mixture of the first sorted material and the additive istransferred to the accumulating unit 60 through the pipe 54.

The accumulating unit 60 introduces the mixture having passed throughthe mixing unit 50 from the introduction port 62, loosens the defibratedmaterial of the entangled cellulose fibers, and drops the mixture whiledispersing the mixture in the air. In this manner, the accumulating unit60 can uniformly accumulate the mixture on the second web forming unit70.

The accumulating unit 60 includes a drum portion 61 and a housing unit63 that accommodates the drum portion 61. A cylindrical rotating sieveis used as the drum portion 61. The drum portion 61 has a net and dropsthe cellulose fibers or particles which are contained in the mixturehaving passed through the mixing unit 50 and have a size smaller thanthe size of the mesh of the net. The configuration of the drum portion61 is the same as the configuration of the drum portion 41.

Further, “sieve” of the drum portion 61 may not have a function ofsorting out a specific object. That is, “sieve” used as the drum portion61 denotes a portion provided with a net, and the drum portion 61 maydrop the entire mixture introduced to the drum portion 61.

The second web forming unit 70 accumulates the material having passedthrough the accumulating unit 60 to form a web W which is an accumulatedmaterial serving as the buffer material WS. Here, a molding die which isnot shown in FIG. 1 is placed on the mesh belt 72 to be used as a saucerso that a web can be formed in the molding die. The second web formingunit 70 includes the mesh belt 72, the stretching roller 74, and thesuction mechanism 76.

Any of the molding dies having shapes shown in FIGS. 2A, 2B, 2C, and 2Dcan be used as the molding die. When the buffer material WS has athree-dimensional shape having a projection, such as a bombshell shape,a hemispherical shape, a laterally-long elliptical shape, a speakershape, a cylindrical shape, a conical shape, or step-like conical shape,since the buffer material is capable of more suitably withstanding animpact, the shape thereof can be optionally changed.

The mesh belt 72 accumulates the material having passed through theopening of the accumulating unit 60, that is, the opening of the net onthe molding die while moving. The mesh belt 72 and the molding die areconfigured to be stretched by the stretching roller 74 and circulate theair to make the material having passed through the accumulating unitdifficult to pass through. The mesh belt 72 moves by rotation of thestretching roller 74. The mesh belt 72 continuously drops andaccumulates the material having passed through the accumulating unit 60while continuously moving, and thus the web W is formed on the moldingdie provided on the mesh belt 72. The mesh belt 72 and the molding dieare made of, for example, a metal, a resin, cloth, or nonwoven fabric.

The suction mechanism 76 is provided below the mesh belt 72, that is, ona side opposite to the side of the accumulating unit 60. The suctionmechanism 76 can generate an air flow flowing downward, that is, an airflow flowing to the mesh belt 72 from the accumulating unit 60. Themixture dispersed in the air by the accumulating unit 60 can be suckedonto the mesh belt 72 by the suction mechanism 76. In this manner, thedischarge rate of the material from the accumulating unit 60 can beincreased. Further, the suction mechanism 76 can form a downflow in thepath where the mixture falls, and thus it is possible to suppress thedefibrated material and the additive from being entangled with eachother during the fall.

As described above, the web W is formed in a soft and inflated state dueto containing a large amount of air by carrying out the web forming stepperformed by the accumulating unit 60 and the second web forming unit70. The web W accumulated on the molding die provided on the mesh belt72 is transported to the buffer material forming unit 80.

The thickness of the web W which is the accumulated material to betransported to the buffer material forming unit 80 is preferably 2.0 mmor greater and 150 mm or less, more preferably 3.0 mm or greater and 120mm or less, and still more preferably 5.0 mm or greater and 100 mm orless.

Further, the density of the web W is preferably 0.01 g/cm³ or greaterand 0.05 g/cm³ or less and more preferably 0.02 g/cm³ or greater and0.04 g/cm³ or less.

Further, the basis weight of the web W is preferably 20 g/m² or greaterand 7500 g/m² or less, more preferably 30 g/m² or greater and 6000 g/m²or less, and still more preferably 50 g/m² or greater and 5000 g/m² orless.

The buffer material forming unit 80 forms the buffer material WS byheating the web W accumulated on the molding die provided on the meshbelt 72. The buffer material forming unit 80 heats the web W which isthe accumulated material of the mixture of the defibrated material andthe additive mixed in the second web forming unit 70, and thus thenatural binding material is softened and melted. In this manner, theplurality of cellulose fibers are bound to each other.

The buffer material forming unit 80 includes a heating unit 84 thatheats the web W. For example, a heat press or a heating roller may beused as the heating unit 84, and an example of using a heating rollerwill be described below. The number of heating rollers in the heatingunit 84 is not particularly limited. In the example shown in the figure,the heating unit 84 includes a pair of heating rollers 86. The buffermaterial WS can be molded while the web W is continuously transported byconfiguring the heating unit 84 as the heating rollers 86.

The heating rollers 86 are disposed such that the rotation axes thereofare in parallel with each other. The roller radius of the heating roller86 is preferably 2.0 cm or greater and 5.0 cm or less, more preferably2.5 cm or greater and 4.0 cm or less, and still more preferably 2.5 cmor greater and 3.5 cm or less.

The heating rollers 86 come into contact with the web W and heat the webW while transporting the web W in a state of interposing the web W.

The rotation speed of the heating rollers 86 is, for example, preferably20 rpm or greater and 500 rpm or less, more preferably 30 rpm or greaterand 350 rpm or less, and still more preferably 50 rpm or greater and 300rpm or less.

In this manner, the surface region of the web W can be sufficientlyheated with high accuracy.

The heating rollers 86 transport the web W in a state of interposing theweb W to form the buffer material WS having a predetermined thickness.

Here, the pressure applied to the web W by the heating rollers 86 ispreferably 0.50 MPa or less, more preferably 0.01 MPa or greater and0.45 MPa or less, and still more preferably 0.05 MPa or greater and 0.40MPa or less.

The surface temperature of the heating rollers 86 when heating the web Wis preferably 160° C. or higher, more preferably 165° C. or higher and250° C. or lower, and still more preferably 170° C. or higher and 220°C. or lower.

It is preferable that the gap between the pair of heating rollers 86 ofthe heating unit 84 be adjusted such that the thickness, the density,and the basis weight of the buffer material WS satisfy the conditionsdescribed in the section 1-4.

The production device 100 of the present embodiment may include thecutting unit 90 as necessary. In the example shown in the figure, thecutting unit 90 is provided on the downstream of the heating unit 84.The cutting unit 90 cuts the molding die containing the buffer materialWS molded by the buffer material forming unit 80. In the example shownin the figure, the cutting unit 90 includes a first cutting unit 92cutting the molding die of the buffer material WS in a directionintersecting the transport direction of the buffer material WS and asecond cutting unit 94 cutting the buffer material WS in a directionparallel to the transport direction. The second cutting unit 94 cuts,for example, the molding die containing the buffer material WS havingpassed through the first cutting unit 92.

Further, the production device 100 of the present embodiment may includethe humidifying unit 78. In the example shown in the figure, thehumidifying unit 78 is provided on the downstream of the cutting unit 90and on the upstream of a discharge unit 96. The humidifying unit 78 iscapable of applying water or water vapor to the buffer material WS.Specific examples of the aspect of the humidifying unit 78 include anaspect of spraying mist of water or an aqueous solution, an aspect ofspraying water or an aqueous solution, and an aspect of jetting water oran aqueous solution from an ink jet head for adhesion.

Since the production device 100 includes the humidifying unit 78, thebuffer material WS to be formed can be humidified. In this manner, thecellulose fibers are humidified and softened. Therefore, when acontainer or the like is three-dimensionally molded by using the buffermaterial WS, wrinkles or breakage is less likely to occur. Further,since a hydrogen bond is easily formed between cellulose fibers byhumidifying the buffer material WS, the density of the buffer materialWS is increased, and for example, the strength can be improved.

In the example of FIG. 1 , the humidifying unit 78 is provided on thedownstream of the cutting unit 90, and the same effects as describedabove can be obtained as long as the humidifying unit 78 is provided onthe downstream of the heating unit 84. That is, the humidifying unit 78may be provided on the downstream of the heating unit 84 and on theupstream of the cutting unit 90.

The buffer material WS is obtained, for example, as a three-dimensionalmolded body having a convex shape by demolding only the buffer materialWS from the molding die where the buffer material WS has been molded.

Hereinbefore, the suitable embodiments of the present disclosure havebeen described, but the present disclosure is not limited thereto.

For example, the present disclosure has configurations that aresubstantially the same as the configurations described in theembodiments, for example, configurations with the same functions, thesame methods, and the same results as described above or configurationswith the same purposes and the same effects as described above. Further,the present disclosure has configurations in which parts that are notessential in the configurations described in the embodiments have beensubstituted. Further, the present disclosure has configurationsexhibiting the same effects as the effects of the configurationsdescribed in the embodiments or configurations capable of achieving thesame purposes as the purposes of the configurations described in theembodiments. Further, the present disclosure has configurations in whichknown techniques have been added to the configurations described in theembodiments.

For example, the buffer material of the present disclosure is notlimited to the buffer material produced by the above-described methodusing the above-described production device.

More specifically, for example, the case where the buffer material isproduced by using the composition for producing a buffer material thatis the composition containing the cellulose fibers and the naturalbinding material has been described as a representative example in theabove-described embodiments, but the buffer material may be produced bysprinkling the natural binding material on the cellulose fibers whichhave been prepared in advance and heating and pressing the cellulosefibers and the natural binding material.

EXAMPLES

Hereinafter, the present disclosure will be described in more detailwith reference to examples and comparative examples, but the presentdisclosure is not limited to the following examples.

3. Production of Buffer Material Example 1

A buffer material was produced using corrugated cardboard (manufacturedby Rengo Co., Ltd.) as a raw material that was a cellulose fiber source,using Chinese shellac resin powder having a softening point of 62° C., acuring point of 152° C., and a volume average particle diameter of 20 μmor less as a natural binding material, and using a production device fora buffer material with the configuration shown in FIG. 1 . Here, a #3type molding die with a plurality of hemispherical recesses arranged ina staggered manner and a #3 type molding die with a plurality ofhemispherical projections corresponding to the recesses and arranged ina staggered manner were used. Further, the content of lignin in thecellulose fibers was 1.0% by mass or less. Further, the supply amount ofthe natural binding material was adjusted such that the blending ratiobetween the cellulose fibers and the natural binding material in thebuffer material produced reached 70% by mass:30% by mass. In addition,the heating temperature, the pressing pressure, and the heating andpressing time in the buffer material forming unit were respectivelyadjusted to 170° C., 0.05 MPa, and 60 seconds.

The buffer material produced had a thickness of 3.5 mm, a density of0.05 g/cm³, and a basis weight of 175 g/m². Further, the cellulosefibers contained in the buffer material had an average thickness of 730μm and an average thickness of 20 μm.

Examples 2 to 4

Each buffer material was produced in the same manner as in Example 1except that the supply amount of the natural binding material waschanged such that the blending ratio between the cellulose fibers andthe natural binding material in the buffer material produced was set aslisted in Table 1.

Examples 5 to 8

Each buffer material was produced in the same manner as in Example 1except that the conditions for the buffer material forming unit wereadjusted and the density of the buffer material was set as listed inTable 1. Comparative Example 1 and 2

Each buffer material was attempted to be produced in the same manner asin Example 1 except that the supply amount of the natural bindingmaterial was changed such that the blending ratio between the cellulosefibers and the natural binding material in the buffer material producedwas set as listed in Table 1.

The configurations of the buffer materials in the examples and thecomparative examples are collectively listed in Table 1.

TABLE 1 Conditions for Constituent component buffer material Cellulosefibers Shellac resin Density [% by mass] [% by mass] [g/cm³] Example 170 30 0.05 Example 2 80 20 0.05 Example 3 85 15 0.05 Example 4 90 100.05 Example 5 70 30 0.02 Example 6 70 30 0.10 Example 7 70 30 0.20Example 8 70 30 0.30 Comparative 95 5 0.05 Example 1 Comparative 60 400.40 Example 2

4. Evaluation 4-1. Moldability

In each example and each comparative example, a case where a buffermaterial having a shape corresponding to the shape of the molding diewas able to be produced was evaluated as “possible”, and a case where abuffer material having a shape corresponding to the shape of the moldingdie was not able to be produced was evaluated as “impossible”.

4-2. Stress/Strain Curve

The buffer material was compressed in the thickness direction, that is,the projection direction of a hemispherical projection using a universaltest machine AG-IS (manufactured by Shimadzu Corporation), and astress/strain curve was created. That is, a graph showing therelationship between the ratio of the thickness of the buffer materialduring the compression to the thickness of the buffer material in anatural state and the stress applied during the compression was created.

4-3. Buffer Coefficient/Strain Curve

The buffer material was compressed in the thickness direction, that is,the projection direction of a hemispherical projection using a universaltest machine AG-IS (manufactured by Shimadzu Corporation), and a buffercoefficient/strain curve was created. That is, a graph showing therelationship between the ratio of the thickness of the buffer materialduring the compression to the thickness of the buffer material in anatural state and the buffer coefficient during the compression wascreated.

The results of the section 4-1 for each example and each comparativeexample are listed in Table 2, the results of the section 4-2 forExamples 1 to 4 are shown in FIG. 3 , the results of the section 4-2 forExamples 5 to 8 are shown in FIG. 4 , the results of the section [4-3]for Examples 1 to 4 are shown in FIG. 5 , and the results of the section4-3 for Examples 5 to 8 are shown in FIG. 6 .

TABLE 2 Moldability Example 1 Possible Example 2 Possible Example 3Possible Example 4 Possible Example 5 Possible Example 6 PossibleExample 7 Possible Example 8 Possible Comparative Example 1 ImpossibleComparative Example 2 Impossible

As is evident in Table 2, it was found that in each example, a buffermaterial having a desired shape was able to be produced and hadexcellent moldability.

Further, as is evident in FIGS. 3 and 4 , it was found that in eachexample, the stress was almost constant in a wide range of strain, andthe buffer material had excellent buffering performance.

Further, when buffer materials were produced in the same manner as ineach example described above except that the average length of thecellulose fibers contained in the buffer materials was changed within arange of 10 μm or greater and 50 mm or less, the average thicknessthereof was changed within a range of 1.0 μm or greater and 1000 μm orless, and the average aspect ratio thereof was changed within a range of10 or greater and 1000 or less and the evaluations were performed in thesame manners as described above, results similar to those describedabove were obtained.

What is claimed is:
 1. A buffer material comprising: cellulose fibers;and a binding material that binds the cellulose fibers, wherein thebinding material is a natural component and a proportion of the bindingmaterial in the buffer material is 10.0% by mass or greater and 30.0% bymass or less.
 2. The buffer material according to claim 1, wherein thebinding material contains a shellac resin.
 3. The buffer materialaccording to claim 1, wherein the buffer material has a thickness of 1.0mm or greater and 100 mm or less, and the buffer material has a densityof 0.02 g/cm³ or greater and 0.20 g/cm³ or less.
 4. The buffer materialaccording to claim 1, wherein a content of lignin in the cellulosefibers is 5.0% by mass or less.